Question

A galvanometer with a scale divided into $100$ equal divisions has a current sensitivity of $10$ divisions per milliampere and a voltage sensitivity of $2$ divisions per millivolt. The galvanometer resistance will be

• A. $4 \, \Omega $
• B. $5 \, \Omega $
• C. $3 \, \Omega $
• D. $7 \, \Omega $

Answer 1

Answer: (B)

Here, the current sensitivity is $10div/mA$ and there are $100$ divisions on the scale. So, the current required for full-scale deflection is
$I_{g}=\frac{1}{10}\times 100mA=10mA$
$=0.01A$
Also, the voltage sensitivity is $2 \, div/mV$ so the voltage required for full-scale deflection is
$V_{g}=\frac{1}{2}\times 100 \, mV$
$=0.05V$
Galvanometer resistance is given by
$G=\frac{V_{g}}{I_{g}}=\frac{0.05}{0.01}$
$=5\Omega \, $